Neurofibromas are a common type of peripheral nerve sheath tumour that develops on peripheral nerves that contain fibrous or connective tissue. They are generally benign (non-cancerous), solitary and sporadic (develop randomly without a genetic predisposition).
Peripheral nerve sheath tumours (PNSTs) are tumours that arise from the protective layer of peripheral nerves. More specifically, they develop from nerve sheaths, which are layers of myelin and connective tissue that provide insulation to nerve fibres within the nervous system.
The nervous system is made up of two primary components: the central nervous system (CNS), and the peripheral nervous system (PNS). The CNS is made up of the brain and spinal cord, and is responsible for all sensory and motor functions in the body. The PNS encompasses all nerves outside of the CNS, and is responsible for all involuntary functions in the body. The PNS is further subdivided into the autonomic nervous system (ANS) and the somatic nervous system (SNS). The ANS controls involuntary processes and glands, such as heart rate, blood pressure, respiration, and digestion. Comparatively, the SNS is responsible for voluntary and involuntary muscle movements, as well as transmitting sensory information to the CNS.
Neurofibromas are generally diagnosed equally among the sexes, and are generally diagnosed in people between the ages of 20-40. However, anyone can develop this disease.
Types of Neurofibromas
There are four primary types of neurofibroma, which are classified by the types of cells they develop from.
Intraneural Neurofibroma
Intraneural neurofibromas are the most common subtype of neurofibroma, and is categorised by the tumour developing inside the centre of the nerve. These tumours are generally found in patients between the ages of 20-30, and can be localised (contained in one area) and/or nodular. Intraneural neurofibromas are generally benign, and can have a good prognosis.
Localised/Nodular Cutaneous Neurofibroma
Localised and nodular cutaneous neurofibromas are a less common subtype of neurofibroma that develops within the dermis (middle layer of the skin) and subcutaneous tissue (fatty tissue layer beneath the skin). These tumours are generally found in patients between the ages of 20-30, and can develop in any area of the body. Localised and nodular cutaneous neurofibromas are often benign, and can have a good prognosis.
Diffuse Cutaneous Neurofibroma
Diffuse cutaneous neurofibroma are a rare subtype of neurofibroma that develops within subcutaneous tissue beneath the skin. However, unlike localised cutaneous neurofibroma, these tumours are not well contained (or diffuse), and are generally diagnosed in children and young adults. Diffuse cutaneous neurofibromas are commonly misdiagnosed as plexiform neurofibroma, however these tumours are less likely to become cancerous. These tumours are generally benign, and can have a good prognosis.
Plexiform Neurofibroma
Plexiform neurofibromas are a rare subtype of neurofibroma that develops within the subcutaneous tissue beneath the skin, and are commonly confused with diffuse cutaneous neurofibromas. These tumours are generally diagnosed in early childhood, and have a strong association to neurofibromatosis type 1 (NF1). Plexiform neurofibromas tend to develop deeper into nerves and plexuses, and have a higher chance of undergoing a malignant transformation.
Treatment
When cancers are detected, they are staged and graded based on size, metastasis (whether the cancer has spread to other parts of the body), and how the cancer cells look under the microscope. Staging and grading helps your doctors determine the best treatment for you. However, as the neurofibromas are considered benign, these tumours are generally considered low-grade and not staged.
Once your tumour has been diagnosed, your doctor may recommend genetic testing, which analyses your tumour DNA and can help determine which treatment has the greatest chance of success. They will then discuss the most appropriate treatment option for you.
Treatment is dependent on several factors, including location, age, stage of disease and overall health.
Treatment options for neurofibromas may include:
- Surgery to remove as much of the tumour as possible.
- Watch and wait.
- Radiation therapy.
- Clinical trials.
- Palliative care.
For more information on the treatment options, please refer to the Rare Cancers Australia treatment options page.
Risk factors
While the cause of neurofibromas remain unknown, the following factors may increase the likelihood of developing the disease.
Not everyone with these risk factors will develop the disease, and some people who have the disease may have none of these risk factors. See your general practitioner (GP) if you are concerned.
Early symptoms
Neurofibromas may appear asymptomatic in the early stages of disease. If the tumour becomes malignant, or if the tumour is pressing on a nerve, you may experience:
- Pain in the affected area.
- Numbness and/or tingling in the affected area.
- Weakness and/or loss of function in affected area.
- Small, pea-shaped lumps under the skin.
Not everyone with the symptoms above will have cancer, but see your general practitioner (GP) if you are concerned.
Diagnosis/diagnosing
If your doctor suspects you have a neurofibroma, they may order the following tests to confirm the diagnosis and refer you to a specialist for treatment.
Physical examination
Your doctor will collect your overall medical history, as well as your current symptoms. Following this, they may examine your body to check for any abnormalities.
Neurological examination
A neurological examination assesses sensory and motor functions, and can generally be done in your GPs office. The doctor may check your vision, hearing, balance, coordination, strength, and reflexes, depending on the signs and symptoms you have described. Any problem that is detected in this exam can help determine which portion of the CNS needs further investigation.
Imaging & Blood tests
The doctor will take images of your body using magnetic resonance imaging (MRI), a computed tomography scan (CT scan), x-rays, bone scan and/or positron emission tomography (PET scan), depending on where it is suspected the cancer is. The doctor may also look at other parts of the body and look for signs of metastasis. Additionally, a blood test may be taken to assess your overall health and help guide treatment decisions.
Electromyogram (EMG)
An electromyogram is a diagnostic procedure used to measure the response of nerves and skeletal muscles to electrical activity. For this test, small needles are inserted into your muscle and records the electrical activity in the muscle as you try to move it. This procedure is often performed by a specialist, and is often performed while you are awake.
Nerve Conduction Study
A nerve conduction study, also known as a nerve conduction velocity test, is a diagnostic procedure used to measure the speed of electrical impulses through a nerve. The test involves stimulating the nerves via small electrode patches on the skin with a very small electrical impulse. Nerve conduction studies are often performed alongside an EMG.
Biopsy
Once the location of the cancer has been identified, the doctor will perform a biopsy to remove a section of tissue using a needle. This tissue will then be sent to the lab and analysed for cancer cells.
Prognosis (Certain factors affect the prognosis and treatment options)
While it is not possible to predict the exact course of the disease, your doctor may be able to give you a general idea based on the rate and depth of tumour growth, susceptibility to treatment, age, overall fitness, and medical history. Generally, neurofibromas have a good prognosis and survival rates. However, if the tumour has become malignant and/or has spread, the prognosis may not be as good, and there may be a higher risk of recurrence. It is very important to discuss your individual circumstances with your doctor to better understand your prognosis.
References
Some references are to overseas websites. There may be references to drugs and clinical trials that are not available here in Australia.